The Veterinary Medicine Resource, part of the Laboratory Animal Sciences program, supports The Jackson Laboratory (TJL) Cancer Center investigators by ensuring the health and productivity of their mice. This is accomplished through: 1) a rigorous health and environmental monitoring program; 2) the provision of veterinary care for animals that are injured or suffering from non-infectious disease; and 3) clinical investigations into possible infectious disease problems. In addition, the Veterinary Medicine Resources provides surgically altered mice as requested by Cancer Center investigators. Over the next grant cycle, all Cancer Center mice will be brought to a uniform high health status through a program of rederivation to eliminate several opportunistic microorganisms that are harbored by many TJL research mice. Although not overt pathogens, these microorganisms represent a health threat to immune-deficient mice, and can affect the outcome of research using immunocompetent mice. Rederivation will be performed in conjunction with the Cryopreservation and Rederivation Resource using several approaches, including recovery from cryopreservation, embryo transfer, ovarian transplantation, and hysterectomy derivation. Peggy J. Danneman, V.M.D., M.S., Chief of the Veterinary Medicine Resource and Attending Veterinarian directs all Veterinary Medicine programs and will have primary oversight for the rederivation program. Abigail Smith, Ph.D., Director of Laboratory Animal Sciences, is responsible for overall coordination of the animal health programs. Funds are also requested as partial support for 3 individuals who will be responsible for the day-to-day implementation of the rederivation effort.